Di-alkyl diphenol sulphides



?atented Apr. 2, 1940- UNITED STATES DI-ALKYL DIPHENOL SULPHIDES Louis A. Mikcska and Charles A. Cohen, Elizabeth, N. J., assig'nors to Standard Oil Development Company, a corporation of Delaware No Drawing.

8 Claims. 7

This invention relates to improved oxidation inhibitors which are particularly efiective in the stabilization of mineral oils. This application is a continuation-in-part of Serial No. 51,827 filed November 2'1, 1935, by the present inventors.

It is well known that many phenols and aromatic amines possess the property of retarding the oxidation of certain oils. The common impression exists that most, if not all such compounds will inhibit the oxidation of all-oils, rubber, resins, etc. Recent systematic research on this subject, however, has shown that such a belief is without any reasonable grounds, since as many soluble compounds of the type given can be found to be ineffective or even detrimental in a particular oil, as there are compounds giving beneficial results.

In the case of lubricating oils, although it is generally desirable to employ an oil having a low oxidation rate, at ordinary temperatures, this is not the only important criterion to be considered. The oil must resist injurious oxidation at the high temperatures encountered in the engine as well. It must alsobe free of any tendency.

to settle out sludge or other solid matter in contact with metals (cone test), and must not cause ring sticking or gumming when employed in an engine. Naturally, any inhibitor must be soluble in the oil at the temperatures encountered in practice and not settle out: even at 3.0 or 50 F. Other properties such as the lack of any detrimental eifect upon demulsibility, color, color hold, Conradson carbon, corrosion, viscosity, viscosity index, and gravity are also desirable.

Heretofore, few, if any, single stabilizing agents for lubricants possessed these properties. As a general rule, most oxidation inhibitors seriously affect demulsibility, Conradson carbon and other important properties of lubricants. Attempts have been made by various investigators to employ mixtures of different inhibitors to eliminate this result, but apparently each compound possesses some detrimental property which cannot be overcome by the addition of an auxiliary compound. For instance, many organic compounds possess good inhibiting powers against oxygen absorption, but they form too great a deposit in the cone test (to be described later). Others possess good cone ratings but have little efiect on the oxidation rate. If a mixture of both isemployed, the cone rating is often worse, and furthermore, the Sligh value is generally increased considerably. Many compounds possess a good Sligh Application August 12, 1938, Serial No. 224,540

value but cause exceptionally bad ring sticking in actual engine tests.

An object of this invention, therefore, is to prepare a stabilizing agent for lubricating oils which gives good oxidation inhibiting properties at engine temperature, a good cone rating, little if any ring sticking in engine tests, and substantially no effect upon other properties such as demulsibility, color, Conradson carbon, etc.

The improved oxidation inhibitors of this invention are certain higher alkyl phenol sulphides, and are represented as follows:

aoroosownya' in which R and R represent alkyl groups of 4 to about 8 carbon atoms although larger alkyl groups may also be used. R is preferably the same as R, but may also be a different alkyl group from R. These alkyl groups may be normal or iso, and primary, secondary or tertiary groups. Either or both of the aromatic nuclei may be replaced by naphthyl, anthracyl or other condensed aromatic radicals. The formulae illustrated are purely diagrammatic and the substituent radicals, hydroxyl, alkyl and sulphur, may

be connected to any position in the benzene ring,

but those compounds in which the alkyl radicals are in ortho or para positions to the hydroxyl groups are preferred. Derivatives of these compounds containing additional alkyl, hydroxy and/or sulphur groups, or still other groups such as halogen and CN, which may be connected to either the alkyl groups, the aroride, driving off HCl according to the reaction:

OH OH OH ,Or, it is possible to react a phenol or alkylated phenol with sulphur dichloride to give say, 4:4

media with-alkyl chlorides or dialkyl sulphates,

These ethers, in turn, may then be isomerized in the presence of anhydrous aluminum chloride to the above processes.

produce dialkyl di-phenolthio ethers as in the example:

' Hog-EQUE- Superior stabilizing agents may' be prepared from alkylated phenols obtained by condensation of phenol with the C4 and/or Cs fraction of cracked petroleum hydrocarbons, these being rich in secondary and tertiary olefins of 4 and/or 5 carbon atoms, the alkylated products being converted to the dialkyl thio ethers by any of The seconda'ry'oleflns may be separated from the tertiary, and condensed separately to produce-corresponding mixed disecondary or di-tertiary' thio ethers.

The crude stabilizing agents formed by the above methods may be further purified by distillation, extraction, treating with clay, acid, etc.

The compounds prepared according to this invention greatly stabilize mineral lubricating oils at elevated temperatures, especially the highly refined oils such as synthetic oils, solvent extracted oils obtained by treatment of mineral lubricating oils with single solvents such as phenol, dichlorethyl ether, furfural, propane, nitrobenzene, crotonaldehyde, etc., or by double or multiple solvents such as propane-cresol, etc., clay or acid treated oils, also aluminum chloride treated oils, white oils, hydrogenated oils, and the like, and to the greatest extent such oils having adsorptive agents, as well as coal tar or shale distillates, pale oils, neutrals, bright stocks and other residual stocks, cracking coil tar fractions,

condensed or polymerized fractions, and the like, either waxy, dewaxed, or non-waxy.

The compounds prepared according to this invention may also be used as oxidation inhibitors generally in organic materialswhich are subject to degradation by oxidation during normal conditions, or which tend to deteriorate by absorption of oxygen from the air. Illustrations of such materials are fatty oils, petroleum oils and their derivatives, soaps, aldehydes, synthetic resins, rubber, synthetic rubber, paper, and the like.

The stabilizing agents prepared according to this invention are generally employed in pro-.- portions below 1%, say 0.5%, 0.2%, 0.1% or even 0.05% or less, although percentages up to 5% are often advantageous in the case of highly unstable oils.

The lubricants and other oxldizable organic materials to which these stabilizing agents are addedmay also contain dyes, metallic or other soaps, pour inhibitors,- sludge dispersers, oxidation inhibitors, thickeners, V. I. improvers such as soluble linear polymers, oiliness agents, resins, rubber, fatty'oils, heat thickened fatty oils, sulphurized fatty oils, extreme pressure lubricating agents, organo-metallic compounds, bright stocks (such as refined petroleum lubricating oil residues), voltolized fats, mineral oils and/or waxes, colloidal solids suchas graphite, zinc oxide, etc., and the like. t

The following examples illustrate suitable methods for preparing the improvedoxidation inhibitors, and also their use in various compo-- sitions:

EXAMPLI I- grams of p-tertiary amyl phenol were tion was added slowly, with stirring, to the boil--v ing solution of amyl phenol. The hydrogen chloride gas evolved during the reaction was withdrawn from the reaction zone through the reflux condenser. sulphur dichloride solution was completed, the boiling of the reaction mixture under reflux was continued for six hours until no further emission of hydrogen chloride was detectable. By this means, all hydrogen chloride is removed and there is no need to wash the reaction product with water. The time of refluxing can be cut down by blowing an inert gas'such as nitrogen or flue gas through the reaction mixture. This may be done during the reaction or after all the reagents have been added, as desired.

The solvent, ethylene chloride, was then removed from the reaction mixture by distillation and the resulting product was distilled under a vacuum of 3 mm. mercury absolute pressure. There were thus obtained (1) a fraction distilled below 230 0., consisting of 20-gms, of unreacted phenol, (2) a fraction distilled between 230 and 235 C., and consisting of 108 gms. of

amyl phenol sulphide, and (3) 10 gms. of residue.

The yield of amyl phenol sulphide recovered as distillate was 92.1%, based on the amount of amyl phenol reacting. It is a clear bright yellow liquid which on standing .or being seeded crystallizes to a light yellowsolid. Both the liquid and solid forms are soluble in ether, alcohol, acetone, carbon disulphide, liquid hydrocarbons, hydrocarbon halides, petroleum oils and fractions thereof, including gasoline, kerosene, burning and Diesel oils and lubricating oils, and in most organic solvents.

The residue was easily removable 'from the dis- Qtilling flask with ordinary organic solvents such There was no coke ride in solution in the solvent, the entire volume of solvent may be added initially or as desired,

and the sulphur chloride may be added slowly to the reflux stream.

The equipment in which the reaction is conof ethylene chloride When the addition of the ducted should be non-corrodible by the materials used and the reaction products. It is preferably made of or lined with glass or other acid and Org gen absorptio n test This test is used for the most part in judging the oxidation susceptibility and acid formation of a lubricating oil at elevated temperatures. The

results are generally given in the number of ccs.

of oxygen absorbed by 10 cc. of an oil per 15 minute intervals at 200 C.

Cone test This method is a means for determining the tendency of an oil to deposit solid matter upon heated metallic surfaces. It consists in slowly dropping the oil to be tested over a heated metal (generally steel) cone, having a circumferential groove milled out in a screw fashion on the periphery so as to allow a time of contact of about one minute between the heated steel surface and the oil. A total volume of 60 cc. of oil is dropped from a dropping funnel during a period of 2 hours to obtain this time of contact. The temperature of the cone may be any desired value, but for lubricating oils 250 C. is preferable since it represents approximately the extreme temperature to which oils are exposed in ordinary engine use. The cone is weighed before the test. After all the oil is run over the metal surface, the cone is washed with naphtha to remove adhering oil and the total deposit left is obtained by difference in weight. This value is generally reported in grams. The test does not appear to have any relation to the oxygen absorption test, since it is possible to have two compounds giving the same cone deposit in lubricating oils, but having widely varying oxygen absorption rates, and vice versa.

Ring sticking test This test is often employed to indicate the susceptibility of a lubricating oil to stick rings and gum up pistons in an aviation engine. The oil is employed to lubricate a C. F. R. (Cooperative Fuel Research) engine with a jacket temperature of 390 F. using 2 lbs. of oil for 14 hours, a very severe test for performance under hot conditions. The piston demerit is the rating given based on the general appearance of the pistons; the worse the condition, the higher the value. Usually, a record'is also made of the number of rings stuck as well as the number of degrees of the stuck portion of the piston rings.

Sligh test This test of the tendency of an oil to sludge under oxidizing conditions is described in Proc. A. S. T. M. 24, 964, II (1924), except that the oxidation is conducted for 24 hours.

Demulsibilitu test Lead tolerance test This test is used to determine the tendency of an oil to corrode bearings. It is also known as the Underwood test. 1500 cc. of the oil is maintained at 826 1". and is sprayed for 5 hours against two eadh of copper-lead and cadmium silver alloy bearings. The oil dripplns from the bearing is recirculated. The bearings are weighed before and after the test to determine any loss in weight. The test is then repeated with addition of a soluble lead compound, preferably lead oleate, in increments of 0.005% by weight of lead. A loss in weight of 50 mg. indicates the lead tolerance of the 'oil has beenexceeded, and the amount of lead'added in the previous test is recorded as the "lead tolerance." A lead tolerance below 0.020 is considered unsatisfactory.

Exulru: 2

A lubricating oil obtained by phenol extraction and having a viscosity index of was blended with 0.2% di-tertiary butyl diphenol thio ether. Cone tests on the blend as well as the blank showed that the thio ether stabilized the oil to an exceptional degree (almost 60% reduction in deposit) as can be seen from the data:

833 Reduction Percent Blank 0. 07 Blend 0: 27 59. 5

The blend also showed a marked decrease in oxygen absorption at 200 C., reducing the rate from 218 to 12-13-1417 cc. 02 per 15 min.

- intervals.

Exaurt: 3

A petroleum lubricating oil had the following inspection characteristics: 1

Saybolt viscosity 210 F ..v 90 Ring sticking test:

Piston demerit 6. 33 Skirt demerit 4. 0 No. rings stuck 5 Degrees 1710 This oil was blended with 0.2% di-tertiary butyl diphenol thio ether. The inspection characteristics of this blend were as follows:

The results show the effectiveness of di-tertiary butyl diphenol thio ether in reducing ring sticking to practically a zero value.

' Exams: 4

A sample of petroleum lubricating oil had the following properties:

A. P. I. gravity 29.9 Flash point 465 F. Fire point 525 F.

-Vis. Saybolt F 523 Vis. Saybolt 210 F...... 73.0

Viscosity index 121 Color 2% Rob. Conradson carbon 0.04% Corrosion 210 F. Pass Demulsiblllty 1620 Oxidation rate 200 C 183 cc. 02/ 15 min./10 gm. oil

In um oil was dissolved 0.1 a (ii-tertiary butyl diphenol thio ether. Another series of tests was 4 run. on the blend, and the following data were obtained:

A. P. I. gravity 29.9

Flash point. 465 F.

Fire point 525 F.

We. Saybolt F.-- 528 Vis. Saybolt 210 IL... 73.0

Color 12% Rob.

Conradson carbon 0.04%

Corrosion 210 F Pass Demulsibility 1620 Oxidation rate 200 C- 44-28-26-26 cc. 02/15 -min./10 gm. oil

It will be noted that the oxidation rate of the oil at 200 C. was lowered considerably without affecting in the least any of the other properties of the oil.

EXAMPLE 5 A blend oi 37% phenol treated oil in a neutral stool: suitable as an aviation oil and having a viscosity at 210 F. of 118, showed the following results in the G. F. R. ring sticking test, with and without the addition of 0.2% di-tertiary butyl diphenol thio ether:

Overall dement Gms. carbon Degrees rings stuck in engine 30 15 30 15 59 hrs.

15 hrs. lite.

As the above data show, the addition ot the thio ether showed a great improvement in the appearance of the engine parts as expressed by the overall demerit rating. Also, no rings were stuck with. the blend even after 30 hours opera tion, while in the case of the oil, 1&4? oi the rings were stuck after 15 hours operation. Furthermore. the amount of carbon deposited in the engine was reduced to less than one-half, and the amount of varnish formed (as shown by the varnish demerit) was very little.

Although there have been shown and described 7 certain. specific embodiments of invention, it is apparent that many modifications are poesihle. The invention, therefore, is not to be re stricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim:

1. m alhyl cliphenol sulphides having the m mule no on in which R and R represent alkyl groups having at least four carbon atoms each, x represents an element of the sulphur family, consisting of sulphur, selenium and tellurium.

2. Di-alkyl dlphenol sulphides having the forin which R. represents an alkyl group having from four to five carbon atoms.

4. Di-alkyl diphenol sulphides according to claim 3 in which the carbon atom in each of the said two alkyl groups attached to the phenyl ring is also attached to at least two other carbon atoms of the alkyl group.

5. Di-secondary alkyl diphenol sulphides according to claim 3, in which It represents a secondary alkyl group.

6. Iii-tertiary alkyl diphenol sulphides according to claim 3, in which R. represents a tertiary alkyl group.

"i. Di-tertiary butyl diphenol thio ether having the formula substantially as follows:

8. Di-iertiary amyl diphenol thio ether having the formula substantially as follows:

inccca= n30- -c-cm Ha Ha Ha Ha CHARLES A. COHEN. 

